Skip to main content

Full text of "The Cambridge Natural History"

See other formats


EVOLUTION OF THE HORSE

the molar teeth is, too, a little different from that of 'Equ'u.s. Prc
Tiipptis of the North American Pliocene is also three-toed, but
two additionally-developed toes are smaller than in Sippari
Other forms are dealt -with below in connexion with the anees
of Pexissodaetyles. It is a ciraous fact about JKpparion, wli
is not now regarded as on the direct line of equine descent, t'
the edges of the enamel plates of the molars may show a cc
plicated folding very like that presented by that clearly termi
form of Peiissoda^iyle life, the gigantic JSttasynot/iertum* Thif
indicative of high specialisation, •which ended in extinction.

Ancestry  of                      — The   X^ophiodontidae   and   •

Palaeotiieriiilae are two of the most interesting extinct faml
of IPerissodaetyles ; for among them we find what would app
to be the ancestral forms of both the existing Tapirs and Hor
The IRhinocexoses also -would seem to be derivable from
Palaeotheriidae. The very vagueness of the characters of th
creatures, considered from a classifieatory point of view, has led
much diversity in their placing. This though gratifying to
evolutionist is tiresome to the writer who wishes to giv<
methodical account of their various characters. It will be !
perhaps not to attempt an accurate placing or to reconcile c
flicting opinion, but to give some salient features of osteol
which, lead to the belief in their relationship to existing groups
Perissodactyles, A book upon the history of mammals woulc
incomplete without some account of that well- ascertained series
forms which seem to connect these primitive Perissodactyles -?
the modern. Horse. JSq_nuss in fact, is not only the *f show hoi
of the doctrine of evolution, but also the tc stalking horse/'

In the Eocene of both Europe and America are met wil
number of forms from, which we may start. JEfyracotJieri
^regarded on the one hand as the type of a sub-family of
Equidae themselves, and on the other as a member of the far
XxypModontidaa, was a small -sized animal, three feet or so
length ; it possesses the complete Eutherian dentition with a si:
diastema. The orbits are not separated from the temporal fo
the foie-liinbs were four-toed, the Mnd three-toed, with modera
long metapodia, especially on the hind-feet. The shoulder b

Soc. I9OO, p. 370} in tKe cave which, produced ttie renM&isis of
piece of skiai covered with. Fox-red hair, possibly spotted with paler areas, is beE
to be a